Sasha Castel tried to comment on my post of two weeks ago entitled More on Opera and the Constitution, but Movable Type seems to think she's been banned from my site. Since she was unable to get through and the point is important, I'll quote her e-mail here. The question was why so many of the singers and extras in the Met's production of Aïda were wearing blackface or at least beige makeup, though the racial difference between Egyptians and Ethiopians is hardly crucial to the plot. Here is what she wrote:

Actually the Ethiopians are the only ones in blackface. The Egyptians are "Tawny" or tan . . . I know this having been to the supernumerary dressing rooms when body makeup was being applied (and quite a lot of it too).

And your instinct is correct, there is no explicit discussion of racial friction in the libretto of Aida. But it's something the directors do as a sort of visual shorthand, so the audience knows who's who. Interestingly, while most of the black chorus members play the Ethiopian prisoners in the third act, some don't, and can be spotted in light makeup among the Egyptians. Conversely, there are some white and Asian folk among the Ethiopians.

All I can say is that the color scheme didn't look very consistent to me, though I was pretty far from the stage. Among the principals, the Egyptian men all seemed to be darker than the Egyptian women, and the king of Ethiopia seemed no darker than any of the Egyptians. I found it easier to tell who was who by their costumes and dancing: triumphant captors and dejected captives are easy enough to distinguish.

It still seems odd to me, especially compared to the usual practice with other operas, where the singers who portray the six young friends and lovers in La Bohème, to take one obvious example, will often be of five or six different nationalities and two or three different races, as if they lived in Los Angeles in the 21st century rather than Paris in the 19th. Such 'non-traditional' casting doesn't seem to confuse contemporary audiences, and I don't see why it wouldn't work in Aïda as well. (Otello, as I said before, is quite different, since race is fundamental to the plot.)